mfc of change to src/sys/amd64/isa/clock.c breaks build

[Adam Jacob Muller]

This MFC
http://www.freebsd.org/cgi/cvsweb.cgi//src/sys/amd64/isa/clock.c.diff?r1=1.221.2.2;r2=1.221.2.3

of this change:
http://www.freebsd.org/cgi/cvsweb.cgi//src/sys/amd64/isa/clock.c.diff?r1=1.235;r2=1.236

breaks build for LINT, and GENERIC kernels, possibly only on amd64,  
this change was also MFC'd to RELENG_7 but I do not have a 7 amd64 box  
to test.

/usr/src/sys/amd64/isa/clock.c: In function `DELAY':
/usr/src/sys/amd64/isa/clock.c:282: warning: implicit declaration of  
function `cpu_spinwait'
/usr/src/sys/amd64/isa/clock.c:282: warning: nested extern declaration  
of `cpu_spinwait'
*** Error code 1
1 error
*** Error code 2
1 error
*** Error code 2
1 error


- Adam